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Materials, Volume 8, Issue 8 (August 2015), Pages 4631-5553

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Open AccessArticle Microwave Imaging Sensor Using Compact Metamaterial UWB Antenna with a High Correlation Factor
Materials 2015, 8(8), 4631-4651; doi:10.3390/ma8084631
Received: 14 May 2015 / Revised: 2 July 2015 / Accepted: 7 July 2015 / Published: 23 July 2015
Cited by 4 | PDF Full-text (4096 KB) | HTML Full-text | XML Full-text
Abstract
The design of a compact metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. This proposed UWB
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The design of a compact metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. This proposed UWB antenna is made of four metamaterial unit cells, where each cell is an integration of a modified split ring resonator (SRR), capacitive loaded strip (CLS) and wire, to attain a design layout that simultaneously exhibits both a negative magnetic permeability and a negative electrical permittivity. This design results in an astonishing negative refractive index that enables amplification of the radiated power of this reported antenna, and therefore, high antenna performance. A low-cost FR4 substrate material is used to design and print this reported antenna, and has the following characteristics: thickness of 1.6 mm, relative permeability of one, relative permittivity of 4.60 and loss tangent of 0.02. The overall antenna size is 19.36 mm × 27.72 mm × 1.6 mm where the electrical dimension is 0.20 λ × 0.28 λ × 0.016 λ at the 3.05 GHz lower frequency band. Voltage Standing Wave Ratio (VSWR) measurements have illustrated that this antenna exhibits an impedance bandwidth from 3.05 GHz to more than 15 GHz for VSWR < 2 with an average gain of 4.38 dBi throughout the operating frequency band. The simulations (both HFSS and computer simulation technology (CST)) and the measurements are in high agreement. A high correlation factor and the capability of detecting tumour simulants confirm that this reported UWB antenna can be used as an imaging sensor. Full article
Open AccessArticle Influence of Wind Pressure on the Carbonation of Concrete
Materials 2015, 8(8), 4652-4667; doi:10.3390/ma8084652
Received: 20 May 2015 / Revised: 7 July 2015 / Accepted: 20 July 2015 / Published: 24 July 2015
PDF Full-text (2226 KB) | HTML Full-text | XML Full-text
Abstract
Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete
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Carbonation is one of the major deteriorations that accelerate steel corrosion in reinforced concrete structures. Many mathematical/numerical models of the carbonation process, primarily diffusion-reaction models, have been established to predict the carbonation depth. However, the mass transfer of carbon dioxide in porous concrete includes molecular diffusion and convection mass transfer. In particular, the convection mass transfer induced by pressure difference is called penetration mass transfer. This paper presents the influence of penetration mass transfer on the carbonation. A penetration-reaction carbonation model was constructed and validated by accelerated test results under high pressure. Then the characteristics of wind pressure on the carbonation were investigated through finite element analysis considering steady and fluctuating wind flows. The results indicate that the wind pressure on the surface of concrete buildings results in deeper carbonation depth than that just considering the diffusion of carbon dioxide. In addition, the influence of wind pressure on carbonation tends to increase significantly with carbonation depth. Full article
Open AccessArticle Physical Properties of an Ag-Doped Bioactive Flowable Composite Resin
Materials 2015, 8(8), 4668-4678; doi:10.3390/ma8084668
Received: 17 February 2015 / Revised: 12 July 2015 / Accepted: 14 July 2015 / Published: 24 July 2015
Cited by 1 | PDF Full-text (710 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work was to study the physical and antibacterial properties of a flowable resin composite incorporating a sol-gel derived silver doped bioactive glass (Ag-BGCOMP). The depth of the cure was calculated by measuring the surface micro-hardness for the top and
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The aim of this work was to study the physical and antibacterial properties of a flowable resin composite incorporating a sol-gel derived silver doped bioactive glass (Ag-BGCOMP). The depth of the cure was calculated by measuring the surface micro-hardness for the top and bottom surfaces. The volumetric polymerization shrinkage was measured by recording the linear shrinkage as change in length, while the biaxial flexural strength was studied measuring the load at failure. The antibacterial properties of the samples were tested against Streptococcus mutans (S. mutans) and Lactobacillus casei (L. casei). The measured values were slightly decreased for all tested physical properties compared to those of control group (flowable resin composite without Ag-BG), however enhanced bacteria inhibition was observed for Ag-BGCOMP. Ag-BGCOMP could find an application in low stress-bearing areas as well as in small cavity preparations to decrease secondary caries. This work provides a good foundation for future studies on evaluating the effects of Ag-BG addition into packable composites for applications in larger cavity preparations where enhanced mechanical properties are needed. Full article
(This article belongs to the Special Issue Dental Materials)
Open AccessArticle Important Parameter Groups in Thermal Protection of Polymers
Materials 2015, 8(8), 4679-4698; doi:10.3390/ma8084679
Received: 18 June 2015 / Revised: 10 July 2015 / Accepted: 13 July 2015 / Published: 24 July 2015
PDF Full-text (797 KB) | HTML Full-text | XML Full-text
Abstract
The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed
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The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed that encompass the important physical characteristics of each situation and these models are analysed using a mixture of numerical and analytical techniques. Important dimensionless parameter groups are identified and domains of parameter space where thermal performance is particularly good- or particularly bad- are identified. Full article
Open AccessArticle Investigation of the InAs/GaAs Quantum Dots’ Size: Dependence on the Strain Reducing Layer’s Position
Materials 2015, 8(8), 4699-4709; doi:10.3390/ma8084699
Received: 4 June 2015 / Revised: 8 July 2015 / Accepted: 13 July 2015 / Published: 24 July 2015
Cited by 8 | PDF Full-text (1011 KB) | HTML Full-text | XML Full-text
Abstract
This work reports on theoretical and experimental investigation of the impact of InAs quantum dots (QDs) position with respect to InGaAs strain reducing layer (SRL). The investigated samples are grown by molecular beam epitaxy and characterized by photoluminescence spectroscopy (PL). The QDs optical
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This work reports on theoretical and experimental investigation of the impact of InAs quantum dots (QDs) position with respect to InGaAs strain reducing layer (SRL). The investigated samples are grown by molecular beam epitaxy and characterized by photoluminescence spectroscopy (PL). The QDs optical transition energies have been calculated by solving the three dimensional Schrödinger equation using the finite element methods and taking into account the strain induced by the lattice mismatch. We have considered a lens shaped InAs QDs in a pure GaAs matrix and either with InGaAs strain reducing cap layer or underlying layer. The correlation between numerical calculation and PL measurements allowed us to track the mean buried QDs size evolution with respect to the surrounding matrix composition. The simulations reveal that the buried QDs’ realistic size is less than that experimentally driven from atomic force microscopy observation. Furthermore, the average size is found to be slightly increased for InGaAs capped QDs and dramatically decreased for QDs with InGaAs under layer. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
Open AccessArticle Study on Electrochemical Insulin Sensing Utilizing a DNA Aptamer-Immobilized Gold Electrode
Materials 2015, 8(8), 4710-4719; doi:10.3390/ma8084710
Received: 30 June 2015 / Revised: 14 July 2015 / Accepted: 21 July 2015 / Published: 24 July 2015
Cited by 2 | PDF Full-text (433 KB) | HTML Full-text | XML Full-text
Abstract
We investigated an insulin-sensing method by utilizing an insulin-binding aptamer IGA3, which forms an anti-parallel G-quadruplex with folded single strands. Spectroscopic observation indicates that some anti-parallel G-quadruplex bind hemin and show peroxidase activity. In this study, the peroxidase activity of IGA3 with hemin
[...] Read more.
We investigated an insulin-sensing method by utilizing an insulin-binding aptamer IGA3, which forms an anti-parallel G-quadruplex with folded single strands. Spectroscopic observation indicates that some anti-parallel G-quadruplex bind hemin and show peroxidase activity. In this study, the peroxidase activity of IGA3 with hemin was confirmed by spectrophotometric measurements, i.e., the activity was three-times higher than hemin itself. IGA3 was then immobilized onto a gold electrode to determine its electrochemical activity. The peroxidase activity of the immobilized IGA3-hemin complex was determined by cyclic voltammetry, and a cathodic peak current of the electrode showed a dependence on the concentration of H2O2. The cathodic peak current of the IGA3-hemin complex decreased by binding it to insulin, and this decrease depended on the concentration of insulin. Full article
Open AccessArticle Impact of Particle Size of Ceramic Granule Blends on Mechanical Strength and Porosity of 3D Printed Scaffolds
Materials 2015, 8(8), 4720-4732; doi:10.3390/ma8084720
Received: 18 March 2015 / Revised: 21 July 2015 / Accepted: 21 July 2015 / Published: 24 July 2015
Cited by 2 | PDF Full-text (2462 KB) | HTML Full-text | XML Full-text
Abstract
3D printing is a promising method for the fabrication of scaffolds in the field of bone tissue engineering. To date, the mechanical strength of 3D printed ceramic scaffolds is not sufficient for a variety of applications in the reconstructive surgery. Mechanical strength is
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3D printing is a promising method for the fabrication of scaffolds in the field of bone tissue engineering. To date, the mechanical strength of 3D printed ceramic scaffolds is not sufficient for a variety of applications in the reconstructive surgery. Mechanical strength is directly in relation with the porosity of the 3D printed scaffolds. The porosity is directly influenced by particle size and particle-size distribution of the raw material. To investigate this impact, a hydroxyapatite granule blend with a wide particle size distribution was fractioned by sieving. The specific fractions and bimodal mixtures of the sieved granule blend were used to 3D print specimens. It has been shown that an optimized arrangement of fractions with large and small particles can provide 3D printed specimens with good mechanical strength due to a higher packing density. An increase of mechanical strength can possibly expand the application area of 3D printed hydroxyapatite scaffolds. Full article
(This article belongs to the Special Issue Bioceramics)
Open AccessArticle Effects of Different pH-Values on the Nanomechanical Surface Properties of PEEK and CFR-PEEK Compared to Dental Resin-Based Materials
Materials 2015, 8(8), 4751-4767; doi:10.3390/ma8084751
Received: 17 June 2015 / Revised: 13 July 2015 / Accepted: 22 July 2015 / Published: 27 July 2015
Cited by 2 | PDF Full-text (1915 KB) | HTML Full-text | XML Full-text
Abstract
The study determines the stability and durability of polyetheretherketone (PEEK) and a carbon fiber-reinforced PEEK (CFR-PEEK) with 30% short carbon fibers, a dental composite based on Bis-GMA and polymethylmethacrylate (PMMA) under the influence of different pH-values of the oral environment in vitro.
[...] Read more.
The study determines the stability and durability of polyetheretherketone (PEEK) and a carbon fiber-reinforced PEEK (CFR-PEEK) with 30% short carbon fibers, a dental composite based on Bis-GMA and polymethylmethacrylate (PMMA) under the influence of different pH-values of the oral environment in vitro. Nanomechanical properties were investigated by nanoindentation and nanoscratch tests before and after incubation of the specimens at 37 °C for 30 days in artificial saliva with pH-values of 3, 7 and 10, respectively. Nanoindentation and nanoscratching tests were performed using the Hysitron TI950 TriboIndenter to evaluate the reduced elastic moduli, nanohardness, viscoelasticity, friction coefficient and residual scratch profiles. After treatment, the nanomechanical properties of unfilled PEEK did not change. The reduced elastic moduli and nanohardness of the carbon fiber-reinforced PEEK increased significantly. The reduced elastic moduli and nanohardness of CHARISMA decreased. The plasticity of all materials except that of the unfilled PEEK increased. This indicates that different pH-values of the artificial saliva solutions had no obvious influences on the nanomechanical properties of the PEEK matrix. Therefore, the aging resistance of the unfilled PEEK was higher than those of other materials. It can be deduced that the PEEK matrix without filler was more stable than with filler in the nanoscale. Full article
Open AccessArticle Soft X-ray Exposure Promotes Na Intercalation in Graphene Grown on Si-Face SiC
Materials 2015, 8(8), 4768-4777; doi:10.3390/ma8084768
Received: 11 June 2015 / Revised: 17 July 2015 / Accepted: 21 July 2015 / Published: 28 July 2015
Cited by 1 | PDF Full-text (1946 KB) | HTML Full-text | XML Full-text
Abstract
An investigation of how electron/photon beam exposures affect the intercalation rate of Na deposited on graphene prepared on Si-face SiC is presented. Focused radiation from a storage ring is used for soft X-ray exposures while the electron beam in a low energy electron
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An investigation of how electron/photon beam exposures affect the intercalation rate of Na deposited on graphene prepared on Si-face SiC is presented. Focused radiation from a storage ring is used for soft X-ray exposures while the electron beam in a low energy electron microscope is utilized for electron exposures. The microscopy and core level spectroscopy data presented clearly show that the effect of soft X-ray exposure is significantly greater than of electron exposure, i.e., it produces a greater increase in the intercalation rate of Na. Heat transfer from the photoelectrons generated during soft X-ray exposure and by the electrons penetrating the sample during electron beam exposure is suggested to increase the local surface temperature and thus the intercalation rate. The estimated electron flux density is 50 times greater for soft X-ray exposure compared to electron exposure, which explains the larger increase in the intercalation rate from soft X-ray exposure. Effects occurring with time only at room temperature are found to be fairly slow, but detectable. The graphene quality, i.e., domain/grain size and homogeneity, was also observed to be an important factor since exposure-induced effects occurred more rapidly on a graphene sample prepared in situ compared to on a furnace grown sample. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
Open AccessArticle Evaluation and Description of Friction between an Electro-Deposited Coating and a Ceramic Ball under Fretting Condition
Materials 2015, 8(8), 4778-4789; doi:10.3390/ma8084778
Received: 7 June 2015 / Revised: 22 July 2015 / Accepted: 23 July 2015 / Published: 28 July 2015
Cited by 2 | PDF Full-text (1454 KB) | HTML Full-text | XML Full-text
Abstract
This article describes fretting behavior of zirconia and silicon nitride balls on an electro-deposited coating. Fretting tests are performed using a ball-on-flat configuration. The evolution of the kinetic friction coefficient is determined, along with slip ratio. Experimental results show that the steady-state friction
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This article describes fretting behavior of zirconia and silicon nitride balls on an electro-deposited coating. Fretting tests are performed using a ball-on-flat configuration. The evolution of the kinetic friction coefficient is determined, along with slip ratio. Experimental results show that the steady-state friction coefficient between ceramic balls (Si3N4 and ZrO2) and an electro-deposited coating is about 0.06, lower than the value between AISI 52100 ball and the coating. After a steady-state sliding, the transition of the friction coefficient is varied with a ball. The friction coefficient for ZrO2 balls became a critical value after higher fretting cycles than those for Si3N4 and AISI 52100 balls. In addition, it is identified that two parameters can describe the transition of the friction coefficient. Finally, the evolution of the friction coefficient is expressed as an exponential or a power-law form. Full article
Open AccessArticle A Near Zero Refractive Index Metamaterial for Electromagnetic Invisibility Cloaking Operation
Materials 2015, 8(8), 4790-4804; doi:10.3390/ma8084790
Received: 31 May 2015 / Revised: 29 June 2015 / Accepted: 7 July 2015 / Published: 29 July 2015
Cited by 11 | PDF Full-text (1014 KB) | HTML Full-text | XML Full-text
Abstract
The paper reveals the design of a unit cell of a metamaterial that shows more than 2 GHz wideband near zero refractive index (NZRI) property in the C-band region of microwave spectra. The two arms of the unit cell were splitted in such
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The paper reveals the design of a unit cell of a metamaterial that shows more than 2 GHz wideband near zero refractive index (NZRI) property in the C-band region of microwave spectra. The two arms of the unit cell were splitted in such a way that forms a near-pi-shape structure on epoxy resin fiber (FR-4) substrate material. The reflection and transmission characteristics of the unit cell were achieved by utilizing finite integration technique based simulation software. Measured results were presented, which complied well with simulated results. The unit cell was then applied to build a single layer rectangular-shaped cloak that operates in the C-band region where a metal cylinder was perfectly hidden electromagnetically by reducing the scattering width below zero. Moreover, the unit cell shows NZRI property there. The experimental result for the cloak operation was presented in terms of S-parameters as well. In addition, the same metamaterial shell was also adopted for designing an eye-shaped and triangular-shaped cloak structure to cloak the same object, and cloaking operation is achieved in the C-band, as well with slightly better cloaking performance. The novel design, NZRI property, and single layer C-band cloaking operation has made the design a promising one in the electromagnetic paradigm. Full article
(This article belongs to the Section Materials for Energy Applications)
Open AccessArticle Enhanced Synthesis of Carbon Nanomaterials Using Acoustically Excited Methane Diffusion Flames
Materials 2015, 8(8), 4805-4816; doi:10.3390/ma8084805
Received: 30 June 2015 / Revised: 23 July 2015 / Accepted: 24 July 2015 / Published: 29 July 2015
Cited by 1 | PDF Full-text (2521 KB) | HTML Full-text | XML Full-text
Abstract
Acoustically modulated methane jet diffusion flames were used to enhance carbon nanostructure synthesis. A catalytic nickel substrate was employed to collect the deposit materials at sampling position z = 10 mm above the burner exit. The fabrication of carbon nano-onions (CNOs) and carbon
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Acoustically modulated methane jet diffusion flames were used to enhance carbon nanostructure synthesis. A catalytic nickel substrate was employed to collect the deposit materials at sampling position z = 10 mm above the burner exit. The fabrication of carbon nano-onions (CNOs) and carbon nanotubes (CNTs) was significantly enhanced by acoustic excitation at frequencies near the natural flickering frequency (ƒ = 20 Hz) and near the acoustically resonant frequency (ƒ = 90 Hz), respectively. At these characteristic frequencies, flow mixing was markedly enhanced by acoustic excitation, and a flame structure with a bright slender core flame was generated, which provided a favorable flame environment for the growth of carbon nanomaterials. The production rate of CNOs was high at 20 Hz (near the natural flickering frequency), at which the gas temperature was about 680 °C. Additionally, a quantity of CNTs was obtained at 70–95 Hz, near the acoustically resonant frequency, at which the gas temperature was between 665 and 830 °C. However, no carbon nanomaterials were synthesized at other frequencies. The enhanced synthesis of CNOs and CNTs is attributed to the strong mixing of the fuel and oxidizer due to the acoustic excitation at resonant frequencies. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle A Double-Negative Metamaterial-Inspired Mobile Wireless Antenna for Electromagnetic Absorption Reduction
Materials 2015, 8(8), 4817-4828; doi:10.3390/ma8084817
Received: 21 May 2015 / Revised: 15 July 2015 / Accepted: 22 July 2015 / Published: 29 July 2015
Cited by 3 | PDF Full-text (3018 KB) | HTML Full-text | XML Full-text
Abstract
A double-negative metamaterial-inspired antenna is presented for mobile wireless applications. The antenna consists of a semi-circular radiating patch and a 3 × 4 hexagonal shaped metamaterial unit cell array in the ground plane. The antenna is fed with a 50 Ω microstrip feed
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A double-negative metamaterial-inspired antenna is presented for mobile wireless applications. The antenna consists of a semi-circular radiating patch and a 3 × 4 hexagonal shaped metamaterial unit cell array in the ground plane. The antenna is fed with a 50 Ω microstrip feed line. The electric dimensions of the proposed antenna are 0.20λ × 0.26λ × 0.004λ, at the low-end frequency. The proposed antenna achieves a −10 dB impedance with a bandwidth of 2.29 GHz at the lower band and 1.28 GHz at the upper band and can operate for most of the mobile applications such as upper GSM bands, WiMAX, Bluetooth, and wireless local area network (WLAN) frequency bands. The focused novelties of the proposed antenna are its small size, multi-standard operating bands, and electromagnetic absorption reduction at all the operating frequencies using the double-negative metamaterial ground plane. Full article
Open AccessArticle Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing
Materials 2015, 8(8), 4829-4842; doi:10.3390/ma8084829
Received: 7 May 2015 / Revised: 16 July 2015 / Accepted: 21 July 2015 / Published: 29 July 2015
Cited by 5 | PDF Full-text (810 KB) | HTML Full-text | XML Full-text
Abstract
A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated
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A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrOx; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N2 ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 1012 cm−2 for as-deposited sample to 4.55 × 1012 cm−2 for the 800 °C annealed one. In addition, the leakage current density increase from about 106 A/cm2 at Vg = +0.5 V for the as-deposited sample to 10−3 A/cm2 at Vg = +0.5 V for the 900 °C annealed one. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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Open AccessArticle Bone Augmentation in Rabbit Tibia Using Microfixed Cobalt-Chromium Membranes with Whole Blood and Platelet-Rich Plasma
Materials 2015, 8(8), 4843-4856; doi:10.3390/ma8084843
Received: 2 May 2015 / Revised: 6 June 2015 / Accepted: 29 June 2015 / Published: 30 July 2015
Cited by 2 | PDF Full-text (886 KB) | HTML Full-text | XML Full-text
Abstract
Background: Bone augmentation is a subject of intensive investigation in regenerative bone medicine and constitutes a clinical situation in which autogenous bone grafts or synthetic materials are used to aid new bone formation. Method: Based on a non-critical defect, Co-Cr barrier membranes were
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Background: Bone augmentation is a subject of intensive investigation in regenerative bone medicine and constitutes a clinical situation in which autogenous bone grafts or synthetic materials are used to aid new bone formation. Method: Based on a non-critical defect, Co-Cr barrier membranes were placed on six adult Fauve de Bourgogne rabbits, divided into two groups: whole blood and PRP. Three densitometric controls were performed during the experiment. The animals were euthanized at 30, 45, 60, and 110 days. The presence of newly formed bone was observed. Samples for histological studies were taken from the augmentation center. Results: External and internal bone tissue augmentation was observed in almost all cases. Significant differences between PRP- and whole blood–stimulated bone augmentation were not observed. At 60 days, bones with PRP presented higher angiogenesis, which may indicate more proliferation and cellular activity. Conclusion: PRP activates the bone regeneration process under optimized conditions by stimulation of osteoblast proliferation after six weeks, when a significant difference in cellular activity was observed. Membranes could stimulate bone augmentation at the site of placement and in the surrounding areas. Full article
(This article belongs to the Special Issue Bioceramics)
Open AccessArticle Environmental and Geotechnical Assessment of the Steel Slags as a Material for Road Structure
Materials 2015, 8(8), 4857-4875; doi:10.3390/ma8084857
Received: 5 May 2015 / Revised: 2 July 2015 / Accepted: 6 July 2015 / Published: 30 July 2015
Cited by 13 | PDF Full-text (1521 KB) | HTML Full-text | XML Full-text
Abstract
Slags are the final solid wastes from the steel industry. Their production from waste and associated materials is a proper implementation of the basic objectives and principles of the waste management. This study aims to investigate the chemical and selected significant geotechnical parameters
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Slags are the final solid wastes from the steel industry. Their production from waste and associated materials is a proper implementation of the basic objectives and principles of the waste management. This study aims to investigate the chemical and selected significant geotechnical parameters of steel slag as the alternative materials used in road construction. These investigations are strongly desired for successful application in engineering. Young’s modules E, and resilient modules Mr showed that their values corresponding with requirements for subbase (principal or auxiliary) and riding surface as well. Tested mechanical properties were conducted in soaked and un-soaked (optimal moisture content) conditions. The designated high content of chromium and zinc are strongly associated with the internal crystal structure of steel slag. The results do not lead to threats when they are applied in roads’ structures. Mechanical characterization was obtained by performing California bearing ratio (CBR) tests for steel slag in fixed compaction and moisture content conditions. Moreover, cyclic loading of steel slag was conducted with the application of cyclic California bearing ratio (cCBR) apparatus to characterization of this material as a controlled low-strength material. Finally, field studies that consist of static load plate VSS tests were presented. Full article
(This article belongs to the Section Porous Materials)
Open AccessCommunication Antibacterial Modification of Kirschner Wires with Polyluteolin toward Methicillin-Resistant Staphylococcus aureus (MRSA)
Materials 2015, 8(8), 4876-4883; doi:10.3390/ma8084876
Received: 20 April 2015 / Revised: 23 June 2015 / Accepted: 10 July 2015 / Published: 30 July 2015
PDF Full-text (468 KB) | HTML Full-text | XML Full-text
Abstract
In this study we report antibacterial modification of Kirschner wires (K-wires) with polyluteolin (PL) toward methicillin-resistant Staphylococcus aureus (MRSA). K-wires were modified by immersing them in the luteolin-containing aqueous solution for 24 h. Characterizations using scanning electron microscopy and electrochemical methods confirmed the
[...] Read more.
In this study we report antibacterial modification of Kirschner wires (K-wires) with polyluteolin (PL) toward methicillin-resistant Staphylococcus aureus (MRSA). K-wires were modified by immersing them in the luteolin-containing aqueous solution for 24 h. Characterizations using scanning electron microscopy and electrochemical methods confirmed the presence of the PL coatings on the K-wires. The PL-coated K-wires were further found to show antibacterial activity toward MRSA and remained unimpaired antibacterial activity even after the steam sterilization treatment. Full article
Open AccessArticle Bone Regeneration and Remodeling within a Unidirectional Porous Hydroxyapatite Bone Substitute at a Cortical Bone Defect Site: Histological Analysis at One and Two Years after Implantation
Materials 2015, 8(8), 4884-4894; doi:10.3390/ma8084884
Received: 11 June 2015 / Revised: 22 July 2015 / Accepted: 27 July 2015 / Published: 30 July 2015
Cited by 4 | PDF Full-text (2844 KB) | HTML Full-text | XML Full-text
Abstract
Unidirectional porous hydroxyapatite (UDPHAp) is an artificial bone substitute with a unique microstructure consisting of 100–300-µm oval pores that present the material unidirectionally. UDPHAp has a compression strength of 14 MPa and a porosity of 75%, which promotes cell migration and capillary formation
[...] Read more.
Unidirectional porous hydroxyapatite (UDPHAp) is an artificial bone substitute with a unique microstructure consisting of 100–300-µm oval pores that present the material unidirectionally. UDPHAp has a compression strength of 14 MPa and a porosity of 75%, which promotes cell migration and capillary formation within the material. Despite these advantageous properties, bone remodeling and bone formation with UDPHAp remain unclear. To examine long-term remodeling and differences in bone formation based on the defect site, trapezoidal prism-shaped UDPHAp blocks were implanted into rectangular-shaped cortical bone defects in the proximal tibia of Japanese white rabbits. Histological analysis performed at 52 and 104 weeks after implantation revealed that bone and capillaries had formed within the implanted UDPHAp material. Bone formed within the UDPHAp implanted in the cortical defect of rabbit tibia and remodel up to two years. The percentage of new bone area within UDPHAp was larger in cortical lesions than that in medullary lesions. These findings suggest that UDPHAp is a promising material for the repair of non-critical-sized cortical bone defects. Full article
(This article belongs to the Special Issue Novel Bone Substitute Materials)
Open AccessArticle Poly(vinyl alcohol) Nanocomposites Reinforced with Bamboo Charcoal Nanoparticles: Mineralization Behavior and Characterization
Materials 2015, 8(8), 4895-4911; doi:10.3390/ma8084895
Received: 14 May 2015 / Revised: 10 July 2015 / Accepted: 16 July 2015 / Published: 31 July 2015
Cited by 16 | PDF Full-text (1633 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polyvinyl alcohol (PVA) demonstrates chemical stability and biocompatibility and is widely used in biomedical applications. The porous bamboo charcoal has excellent toxin absorptivity and has been used in blood purification. In this study, bamboo charcoal nanoparticles (BCNPs) were acquired with nano-grinding technology. The
[...] Read more.
Polyvinyl alcohol (PVA) demonstrates chemical stability and biocompatibility and is widely used in biomedical applications. The porous bamboo charcoal has excellent toxin absorptivity and has been used in blood purification. In this study, bamboo charcoal nanoparticles (BCNPs) were acquired with nano-grinding technology. The PVA and PVA/BCNP nanocomposite membranes were prepared and characterized by the tensile test, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Results showed that the tensile strength and elongation of the swollen PVA membranes containing 1% BCNPs (PB1) were significantly greater than those of PVA and other PVA/BCNP composite membranes. In addition, the major absorption band of OH stretching in the IR spectra shifted from 3262 cm1 for PVA membrane containing 1% BCNP to 3244 cm1 for PVA membrane containing 20% BCNP. This blue shift might be attributed to the interaction between the PVA molecules and BCNPs. Moreover, the intensity of the XRD peaks in PVA was decreased with the increased BCNP content. The bioactivity of the nanocomposites was evaluated by immersion in the simulated body fluid (SBF) for seven days. The mineral deposition on PB5 was significantly more than that on the other samples. The mineral was identified as hydroxyapatite (HA) by XRD. These data suggest that the bioactivity of the composite hydrogel membranes was associated with the surface distribution of hydrophilic/hydrophobic components. The PVA/BCNP composite hydrogels may have potential applications in alveolar bone regeneration. Full article
(This article belongs to the Special Issue Biobased Nanocomposite Functional Materials)
Open AccessArticle Core-Shell-Structured Copolyaniline-Coated Polymeric Nanoparticle Suspension and Its Viscoelastic Response under Various Electric Fields
Materials 2015, 8(8), 4932-4942; doi:10.3390/ma8084932
Received: 1 June 2015 / Revised: 1 June 2015 / Accepted: 24 July 2015 / Published: 3 August 2015
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Abstract
Semi-conducting poly(n-methylaniline) (PNMA)-coated poly(methyl methacrylate) (PMMA) composite nanoparticles were synthesized using cross-linked and grafted PMMA particles as a core, and then, the PNMA shell was coated via chemical oxidative polymerization on the surface of modified PMMA nanoparticles. Their electroresponsive electrorheological characteristics when dispersed
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Semi-conducting poly(n-methylaniline) (PNMA)-coated poly(methyl methacrylate) (PMMA) composite nanoparticles were synthesized using cross-linked and grafted PMMA particles as a core, and then, the PNMA shell was coated via chemical oxidative polymerization on the surface of modified PMMA nanoparticles. Their electroresponsive electrorheological characteristics when dispersed in silicone were confirmed under applied electric fields using a rotational rheometer, focusing on their viscoelastic response. Using a frequency sweep test, the frequency dependence of both the storage and loss moduli was confirmed to increase upon increasing the electric field, with a stable plateau regime over the entire angular frequency range. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle 1,6- and 1,7-Regioisomers of Highly Soluble Amino-Substituted Perylene Tetracarboxylic Dianhydrides: Synthesis, Optical and Electrochemical Properties
Materials 2015, 8(8), 4943-4960; doi:10.3390/ma8084943
Received: 3 July 2015 / Revised: 29 July 2015 / Accepted: 30 July 2015 / Published: 3 August 2015
Cited by 2 | PDF Full-text (2640 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
1,6- and 1,7-regioisomers of diamino-substituted perylene tetracarboxylic dianhydrides (PTCDs) with different n-alkyl chain lengths (n = 6, 12 or 18) were synthesized and characterized by NMR spectroscopy and high-resolution mass spectrometry. These dyes are highly soluble in most organic solvents and even
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1,6- and 1,7-regioisomers of diamino-substituted perylene tetracarboxylic dianhydrides (PTCDs) with different n-alkyl chain lengths (n = 6, 12 or 18) were synthesized and characterized by NMR spectroscopy and high-resolution mass spectrometry. These dyes are highly soluble in most organic solvents and even in nonpolar solvents, such as hexane. To the best of our knowledge, this is the first time the 1,6-diamino-substituted PTCDs (2a2c) have been obtained in pure form. The regioisomers 1a1c (1,7-) and 2a2c (1,6-) exhibit significant differences in their optical characteristics. In addition to the longest wavelength absorption band at around 674 nm, 2a2c exhibit another shoulder band at ca. 600 nm, and consequently, cover a large part of the visible region relative to those of 1a1c. Upon excitation, 2a2c also show larger dipole moment changes than those of 1a1c; the dipole moments of all compounds have been estimated using Lippert–Mataga equation. Moreover, all the dyes show a unique charge transfer emission in the near-infrared region, of which the peak wavelengths exhibit strong solvatochromism. They all exhibit one irreversible one-electron oxidation and two quasi-reversible one-electron reductions in dichloromethane at modest potentials. Complementary density functional theory calculations performed on these chromophores are reported in order to rationalize their electronic structure and optical properties. Full article
(This article belongs to the Special Issue Developments in Organic Dyes and Pigments)
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Open AccessArticle Study on Welding Mechanism Based on Modification of Polypropylene for Improving the Laser Transmission Weldability to PA66
Materials 2015, 8(8), 4961-4977; doi:10.3390/ma8084961
Received: 25 May 2015 / Accepted: 30 July 2015 / Published: 4 August 2015
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Abstract
Polypropylene and PA66 are widely used in our daily life, but they cannot be welded by laser transmission welding (LTW) because of polar differences and poor compatibility. In this paper, grafting modification technology is used to improve the welding performance between polypropylene and
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Polypropylene and PA66 are widely used in our daily life, but they cannot be welded by laser transmission welding (LTW) because of polar differences and poor compatibility. In this paper, grafting modification technology is used to improve the welding performance between polypropylene and PA66. Firstly, the strong reactive and polar maleic-anhydride (MAH) is grafted to polypropylene and infrared spectrometer is used to prove that MAH has been grafted to polypropylene. At the same time, the mechanical and thermal properties of the graft modified polypropylene (TGMPP) are tested. The results prove that the grafting modification has little influence on them. Also, the optical properties of TGMPP are measured. Then, the high welding strength between TGMPP and PA66 is found and the mechanism of the weldability is researched, which shows that there are two reasons for the high welding strength. By observing the micro morphology of the welding zone, one reason found is that the modification of polypropylene can improve the compatibility between polypropylene and PA66 and make them easy to diffuse mutually, which causes many locking structures formed in the welding region. The other reason is that there are chemical reactions between TGMPP and PA66 proved by the X-ray photoelectron spectrometer. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
Open AccessArticle Nanocarbon-Coated Porous Anodic Alumina for Bionic Devices
Materials 2015, 8(8), 4992-5006; doi:10.3390/ma8084992
Received: 7 July 2015 / Revised: 23 July 2015 / Accepted: 3 August 2015 / Published: 5 August 2015
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Abstract
A highly-stable and biocompatible nanoporous electrode is demonstrated herein. The electrode is based on a porous anodic alumina which is conformally coated with an ultra-thin layer of diamond-like carbon. The nanocarbon coating plays an essential role for the chemical stability and biocompatibility of
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A highly-stable and biocompatible nanoporous electrode is demonstrated herein. The electrode is based on a porous anodic alumina which is conformally coated with an ultra-thin layer of diamond-like carbon. The nanocarbon coating plays an essential role for the chemical stability and biocompatibility of the electrodes; thus, the coated electrodes are ideally suited for biomedical applications. The corrosion resistance of the proposed electrodes was tested under extreme chemical conditions, such as in boiling acidic/alkali environments. The nanostructured morphology and the surface chemistry of the electrodes were maintained after wet/dry chemical corrosion tests. The non-cytotoxicity of the electrodes was tested by standard toxicity tests using mouse fibroblasts and cortical neurons. Furthermore, the cell–electrode interaction of cortical neurons with nanocarbon coated nanoporous anodic alumina was studied in vitro. Cortical neurons were found to attach and spread to the nanocarbon coated electrodes without using additional biomolecules, whilst no cell attachment was observed on the surface of the bare anodic alumina. Neurite growth appeared to be sensitive to nanotopographical features of the electrodes. The proposed electrodes show a great promise for practical applications such as retinal prostheses and bionic implants in general. Full article
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Open AccessArticle Raman Spectroscopy of Two-Dimensional Bi2TexSe3 − x Platelets Produced by Solvothermal Method
Materials 2015, 8(8), 5007-5017; doi:10.3390/ma8085007
Received: 26 May 2015 / Revised: 13 July 2015 / Accepted: 27 July 2015 / Published: 5 August 2015
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Abstract
In this paper, we report a facile solvothermal method to produce both binary and ternary compounds of bismuth chalcogenides in the form of Bi2TexSe3 − x. The crystal morphology in terms of geometry and thickness as well
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In this paper, we report a facile solvothermal method to produce both binary and ternary compounds of bismuth chalcogenides in the form of Bi2TexSe3 − x. The crystal morphology in terms of geometry and thickness as well as the stoichiometric ratio can be well controlled, which offers the opportunities to systematically investigate the relationship between microstructure and phonon scattering by Raman spectroscopy. Raman spectra of four compounds, i.e., Bi2Se3, Bi2Se2Te, Bi2SeTe2 and Bi2Te3, were collected at four different excitation photon energies (2.54, 2.41, 1.96, and 1.58 eV). It is found that the vibrational modes are shifted to higher frequency with more Se incorporation towards the replacement of Te. The dependence of Raman vibrational modes on excitation photon energy was investigated. As the excitation photon energy increases, three Raman vibrational modes (A1g1, Eg2 and A1g2) of the as-produced compounds move to low frequency. Three Infrared-active (IR-active) modes were observed in thin topological insulators (TIs) crystals. Full article
Open AccessArticle A Model for Determining Strength for Embedded Elliptical Crack in Ultra-high-temperature Ceramics
Materials 2015, 8(8), 5018-5027; doi:10.3390/ma8085018
Received: 3 June 2015 / Revised: 23 July 2015 / Accepted: 28 July 2015 / Published: 5 August 2015
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Abstract
A fracture strength model applied at room temperature for embedded elliptical crack in brittle solid was obtained. With further research on the effects of various physical mechanisms on material strength, a thermo-damage strength model for ultra-high-temperature ceramics was applied to each temperature phase.
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A fracture strength model applied at room temperature for embedded elliptical crack in brittle solid was obtained. With further research on the effects of various physical mechanisms on material strength, a thermo-damage strength model for ultra-high-temperature ceramics was applied to each temperature phase. Fracture strength of TiC and the changing trends with elliptical crack shape variations under different temperatures were studied. The study showed that under low temperature, the strength is sensitive to the crack shape variation; as the temperature increases, the sensitivities become smaller. The size of ellipse’s minor axes has great effect on the material strength when the ratio of ellipse’s minor and major axes is lower than 0.5, even under relatively high temperatures. The effect of the minor axes of added particle on material properties thus should be considered under this condition. As the crack area is set, the fracture strength decreases firstly and then increases with the increase of ratio of ellipse’s minor and major axes, and the turning point is 0.5. It suggests that for the added particles the ratio of ellipse’s minor and major axes should not be 0.5. All conclusions significantly coincided with the results obtained by using the finite element software ABAQUS. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
Open AccessArticle Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors
Materials 2015, 8(8), 5028-5047; doi:10.3390/ma8085028
Received: 23 June 2015 / Revised: 27 June 2015 / Accepted: 31 July 2015 / Published: 7 August 2015
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Abstract
We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric
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We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material. Full article
(This article belongs to the Special Issue Plasmonic Materials)
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Open AccessArticle Beam Propagation Method Calculating Attenuated Total Reflection Spectra to Excite Hybridized Surface Plasmon Polaritons
Materials 2015, 8(8), 5048-5059; doi:10.3390/ma8085048
Received: 31 March 2015 / Revised: 12 June 2015 / Accepted: 3 August 2015 / Published: 7 August 2015
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Abstract
Using the beam propagation method, an analytical expression of the reflection spectra of a Kretschmann configuration is derived in order to excite hybridized surface plasmonic polaritons (HSPPs). In this configuration, the cladding is a uniaxial dielectric with the optical axis parallel to the
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Using the beam propagation method, an analytical expression of the reflection spectra of a Kretschmann configuration is derived in order to excite hybridized surface plasmonic polaritons (HSPPs). In this configuration, the cladding is a uniaxial dielectric with the optical axis parallel to the interface. The validity of the analytical expression is confirmed by a finite-difference time-domain algorithm and a reported experimental result, respectively. Based on this expression, the properties and the conditions for excitation of the HSPPs are discussed in detail, with regard to the strongly anisotropic cladding and the weakly anisotropic cladding. Full article
(This article belongs to the Special Issue Plasmonic Materials)
Open AccessArticle Enhancing Corrosion and Wear Resistance of AA6061 by Friction Stir Processing with Fe78Si9B13 Glass Particles
Materials 2015, 8(8), 5084-5097; doi:10.3390/ma8085084
Received: 5 July 2015 / Revised: 28 July 2015 / Accepted: 31 July 2015 / Published: 7 August 2015
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Abstract
The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix.
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The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix. The XRD results indicated that the lattice parameter of α-Al increases and the preferred orientation factors F of (200) plane of α-Al reduces after friction stir processing. The coefficient of thermal expansion (CTE) for FSP samples increases at first with the temperature but then decreases as the temperature further increased, which can be explained by the dissolving of Mg and Si from β phase and Fe78Si9B13 particles. The corrosion and wear resistance of FSP samples have been improved compared with that of base metal, which can be attributed to the reduction of grain size and the CTE mismatch between the base metal and reinforced particles by FSP, and the lubrication effect of Fe78Si9B13 particles also plays a role in improving wear resistance. In particular, the FSP sample with reinforced particles in amorphous state exhibited superior corrosion and wear resistance due to the unique metastable structure. Full article
Open AccessArticle Effect of Industrial By-Products on Unconfined Compressive Strength of Solidified Organic Marine Clayey Soils
Materials 2015, 8(8), 5098-5111; doi:10.3390/ma8085098
Received: 25 April 2015 / Revised: 19 July 2015 / Accepted: 31 July 2015 / Published: 7 August 2015
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Abstract
The use of industrial by-products as admixture to ASTM Type I cement (ordinary Portland cement (OPC)) was investigated with the objective of improving the solidification of organic marine clayey soils. The industrial by-products considered in this paper were oyster-shell powder (OSP), steelmaking slag
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The use of industrial by-products as admixture to ASTM Type I cement (ordinary Portland cement (OPC)) was investigated with the objective of improving the solidification of organic marine clayey soils. The industrial by-products considered in this paper were oyster-shell powder (OSP), steelmaking slag dust (SMS) and fuel-gas-desulfurized (FGD) gypsum. The industrial by-products were added to OPC at a ratio of 5% based on dry weight to produce a mixture used to solidify organic marine clayey soils. The dosage ratios of mixtures to organic marine clayey soils were 5, 10 and 15% on a dry weight basis. Unconfined compressive strength (UCS) test after 28 days revealed that the highest strength was obtained with the OPC + SMS 15% mixing ratio. The UCS of specimens treated with this mixture was >500 kPa, compared with 300 kPa for specimens treated with a 15% OPC + OSP mixture and 200 kPa when 15% of OPC was used alone. These results were attributed to the more active hydration and pozzolanic reaction of the OPC + SMS mixture. This hypothesis was verified through X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, and was confirmed by variations in the calcium carbonate (CaCO3) content of the materials during curing. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Work Function Adjustment by Using Dipole Engineering for TaN-Al2O3-Si3N4-HfSiOx-Silicon Nonvolatile Memory
Materials 2015, 8(8), 5112-5120; doi:10.3390/ma8085112
Received: 11 June 2015 / Revised: 3 August 2015 / Accepted: 5 August 2015 / Published: 7 August 2015
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Abstract
This paper presents a novel TaN-Al2O3-HfSiOx-SiO2-silicon (TAHOS) nonvolatile memory (NVM) design with dipole engineering at the HfSiOx/SiO2 interface. The threshold voltage shift achieved by using dipole engineering could enable work function adjustment
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This paper presents a novel TaN-Al2O3-HfSiOx-SiO2-silicon (TAHOS) nonvolatile memory (NVM) design with dipole engineering at the HfSiOx/SiO2 interface. The threshold voltage shift achieved by using dipole engineering could enable work function adjustment for NVM devices. The dipole layer at the tunnel oxide–charge storage layer interface increases the programming speed and provides satisfactory retention. This NVM device has a high program/erase (P/E) speed; a 2-V memory window can be achieved by applying 16 V for 10 μs. Regarding high-temperature retention characteristics, 62% of the initial memory window was maintained after 103 P/E-cycle stress in a 10-year simulation. This paper discusses the performance improvement enabled by using dipole layer engineering in the TAHOS NVM. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Development of Equivalent Material Properties of Microbump for Simulating Chip Stacking Packaging
Materials 2015, 8(8), 5121-5137; doi:10.3390/ma8085121
Received: 15 June 2015 / Revised: 24 July 2015 / Accepted: 4 August 2015 / Published: 7 August 2015
Cited by 2 | PDF Full-text (954 KB) | HTML Full-text | XML Full-text
Abstract
three-dimensional integrated circuit (3D-IC) structure with a significant scale mismatch causes difficulty in analytic model construction. This paper proposes a simulation technique to introduce an equivalent material composed of microbumps and their surrounding wafer level underfill (WLUF). The mechanical properties of this equivalent
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three-dimensional integrated circuit (3D-IC) structure with a significant scale mismatch causes difficulty in analytic model construction. This paper proposes a simulation technique to introduce an equivalent material composed of microbumps and their surrounding wafer level underfill (WLUF). The mechanical properties of this equivalent material, including Young’s modulus (E), Poisson’s ratio, shear modulus, and coefficient of thermal expansion (CTE), are directly obtained by applying either a tensile load or a constant displacement, and by increasing the temperature during simulations, respectively. Analytic results indicate that at least eight microbumps at the outermost region of the chip stacking structure need to be considered as an accurate stress/strain contour in the concerned region. In addition, a factorial experimental design with analysis of variance is proposed to optimize chip stacking structure reliability with four factors: chip thickness, substrate thickness, CTE, and E-value. Analytic results show that the most significant factor is CTE of WLUF. This factor affects microbump reliability and structural warpage under a temperature cycling load and high-temperature bonding process. WLUF with low CTE and high E-value are recommended to enhance the assembly reliability of the 3D-IC architecture. Full article
(This article belongs to the Special Issue Selected Papers from ICETI2014)
Open AccessArticle A Unified Model for the Prediction of Yield Strength in Particulate-Reinforced Metal Matrix Nanocomposites
Materials 2015, 8(8), 5138-5153; doi:10.3390/ma8085138
Received: 9 July 2015 / Revised: 13 July 2015 / Accepted: 5 August 2015 / Published: 10 August 2015
Cited by 10 | PDF Full-text (660 KB) | HTML Full-text | XML Full-text
Abstract
Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such
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Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening) have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs). This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy) in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al2O3, Y2O3, and carbon nanotubes). The predicted results were observed to be in good agreement with the experimental data reported in the literature. Full article
(This article belongs to the Section Advanced Composites)
Open AccessArticle Rheological Analysis of Binary Eutectic Mixture of Sodium and Potassium Nitrate and the Effect of Low Concentration CuO Nanoparticle Addition to Its Viscosity
Materials 2015, 8(8), 5194-5204; doi:10.3390/ma8085194
Received: 10 July 2015 / Revised: 29 July 2015 / Accepted: 3 August 2015 / Published: 11 August 2015
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Abstract
This paper is focused on the characterisation and demonstration of Newtonian behaviour of salt at both high and low shear rate for sodium and potassium nitrate eutectic mixture (60/40) ranging from 250 °C to 500 °C. Analysis of published and experimental data was
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This paper is focused on the characterisation and demonstration of Newtonian behaviour of salt at both high and low shear rate for sodium and potassium nitrate eutectic mixture (60/40) ranging from 250 °C to 500 °C. Analysis of published and experimental data was carried out to correlate all the numbers into one meaningful 4th order polynomial equation. Addition of a low amount of copper oxide nanoparticles to the mixture increased viscosity of 5.0%–18.0% compared to the latter equation. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Growth of Ceria Nano-Islands on a Stepped Au(788) Surface
Materials 2015, 8(8), 5205-5215; doi:10.3390/ma8085205
Received: 22 June 2015 / Accepted: 28 July 2015 / Published: 11 August 2015
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Abstract
The growth morphology and structure of ceria nano-islands on a stepped Au(788) surface has been investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Within the concept of physical vapor deposition, different kinetic routes have been employed to design ceria-Au inverse
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The growth morphology and structure of ceria nano-islands on a stepped Au(788) surface has been investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Within the concept of physical vapor deposition, different kinetic routes have been employed to design ceria-Au inverse model catalysts with different ceria nanoparticle shapes and arrangements. A two-dimensional superlattice of ceria nano-islands with a relatively narrow size distribution (5 ± 2 nm2) has been generated on the Au(788) surface by the postoxidation method. This reflects the periodic anisotropy of the template surface and has been ascribed to the pinning of ceria clusters and thus nucleation on the fcc domains of the herringbone reconstruction on the Au terraces. In contrast, the reactive evaporation method yields ceria islands elongated in [01-1] direction, i.e., parallel to the step edges, with high aspect ratios (~6). Diffusion along the Au step edges of ceria clusters and their limited step crossing in conjunction with a growth front perpendicular to the step edges is tentatively proposed to control the ceria growth under reactive evaporation conditions. Both deposition recipes generate two-dimensional islands of CeO2(111)-type O–Ce–O single and double trilayer structures for submonolayer coverages. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
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Open AccessArticle The Effects of Thermophysical Properties and Environmental Conditions on Fire Performance of Intumescent Coatings on Glass Fibre-Reinforced Epoxy Composites
Materials 2015, 8(8), 5216-5237; doi:10.3390/ma8085216
Received: 29 May 2015 / Revised: 21 July 2015 / Accepted: 28 July 2015 / Published: 11 August 2015
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Abstract
Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable
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Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable steel substrate. The thermal barrier and reaction-to-fire properties of three commercial intumescent coatings on GRE composites have been studied using a cone calorimeter. Their thermophysical properties in terms of heating rate and/or temperature dependent char expansion ratios and thermal conductivities have been measured and correlated. It has been suggested that these two parameters can be used to design coatings to protect composite laminates of defined thicknesses for specified periods of time. The durability of the coatings to water absorption, peeling, impact, and flexural loading were also studied. A strong adhesion between all types of coatings and the substrate was observed. Water soaking had a little effect on the fire performance of epoxy based coatings. All types of 1 mm thick coatings on GRE helped in retaining ~90% of the flexural property after 2 min exposure to 50 kW/m2 heat flux whereas the uncoated laminate underwent severe delamination and loss in structural integrity after 1 min. Full article
Open AccessArticle Effect of Ultraviolet Aging on Rheology and Chemistry of LDH-Modified Bitumen
Materials 2015, 8(8), 5238-5249; doi:10.3390/ma8085238
Received: 23 June 2015 / Revised: 1 August 2015 / Accepted: 4 August 2015 / Published: 12 August 2015
Cited by 3 | PDF Full-text (1011 KB) | HTML Full-text | XML Full-text
Abstract
Layered double hydroxides (LDHs) are an ultravioletlight (UV)-resistant material. In this study, two types of LDHs (Mg-Al-LDHs and Zn-Al-LDHs) were applied to modify bitumen by melt-blending. The effect of ultraviolet aging on the rheology and chemistry of LDH-modified bitumen was studied by means
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Layered double hydroxides (LDHs) are an ultravioletlight (UV)-resistant material. In this study, two types of LDHs (Mg-Al-LDHs and Zn-Al-LDHs) were applied to modify bitumen by melt-blending. The effect of ultraviolet aging on the rheology and chemistry of LDH-modified bitumen was studied by means of dynamic shear rheometer (DSR), thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared spectroscopy (FTIR), and Ultraviolet-Visible (UV-Vis) spectrophotometry to reveal the mechanisms of action for LDHs and bitumen. The results showed that within the UV spectra (220–400 nm), the reflectance of Zn-Al-LDHs was larger than that of Mg-Al-LDHs. These two LDHs have different influences on the performance of bitumen. Mg-Al-LDHs had a more obvious influence on the physical and dynamic rheological properties of bitumen than Zn-Al-LDHs. Zn-Al-LDHs improved the UV-aging resistance of bitumen more. The reason can be that the reflectance of the Zn-Al-LDHs to the UV light is larger than that of the Mg-Al-LDHs. The Zn-Al-LDH-modified bitumen had more potential to improve the UV-aging resistance during the service life of asphalt pavement. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Dislocation-Governed Plastic Deformation and Fracture Toughness of Nanotwinned Magnesium
Materials 2015, 8(8), 5250-5264; doi:10.3390/ma8085250
Received: 15 May 2015 / Revised: 26 July 2015 / Accepted: 4 August 2015 / Published: 13 August 2015
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Abstract
In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in nanotwinned (NT) magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution
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In this work, the plastic deformation mechanisms responsible for mechanical properties and fracture toughness in nanotwinned (NT) magnesium is studied by molecular dynamics (MD) simulation. The influence of twin boundary (TBs) spacing and crack position on deformation behaviors are investigated. The microstructure evolution at the crack tip are not exactly the same for the left edge crack (LEC) and the right edge crack (REC) models according to calculations of the energy release rate for dislocation nucleation at the crack tip. The LEC growth initiates in a ductile pattern and then turns into a brittle cleavage. In the REC model, the atomic decohesion occurs at the crack tip to create a new free surface which directly induces a brittle cleavage. A ductile to brittle transition is observed which mainly depends on the competition between dislocation motion and crack growth. This competition mechanism is found to be correlated with the TB spacing. The critical values are 10 nm and 13.5 nm for this transition in LEC and REC models, respectively. Essentially, the dislocation densities affected by the TB spacing play a crucial role in the ductile to brittle transition. Full article
(This article belongs to the Section Structure Analysis and Characterization)
Open AccessArticle Plant Growth Absorption Spectrum Mimicking Light Sources
Materials 2015, 8(8), 5265-5275; doi:10.3390/ma8085240
Received: 11 June 2015 / Revised: 28 July 2015 / Accepted: 10 August 2015 / Published: 13 August 2015
Cited by 3 | PDF Full-text (1363 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Plant factories have attracted increasing attention because they can produce fresh fruits and vegetables free from pesticides in all weather. However, the emission spectra from current light sources significantly mismatch the spectra absorbed by plants. We demonstrate a concept of using multiple broad-band
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Plant factories have attracted increasing attention because they can produce fresh fruits and vegetables free from pesticides in all weather. However, the emission spectra from current light sources significantly mismatch the spectra absorbed by plants. We demonstrate a concept of using multiple broad-band as well as narrow-band solid-state lighting technologies to design plant-growth light sources. Take an organic light-emitting diode (OLED), for example; the resulting light source shows an 84% resemblance with the photosynthetic action spectrum as a twin-peak blue dye and a diffused mono-peak red dye are employed. This OLED can also show a greater than 90% resemblance as an additional deeper red emitter is added. For a typical LED, the resemblance can be improved to 91% if two additional blue and red LEDs are incorporated. The approach may facilitate either an ideal use of the energy applied for plant growth and/or the design of better light sources for growing different plants. Full article
(This article belongs to the Special Issue Developments in Organic Dyes and Pigments)
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Open AccessArticle Sustained Administration of Hormones Exploiting Nanoconfined Diffusion through Nanochannel Membranes
Materials 2015, 8(8), 5276-5288; doi:10.3390/ma8085241
Received: 1 May 2015 / Revised: 5 August 2015 / Accepted: 5 August 2015 / Published: 13 August 2015
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Abstract
Implantable devices may provide a superior means for hormone delivery through maintaining serum levels within target therapeutic windows. Zero-order administration has been shown to reach an equilibrium with metabolic clearance, resulting in a constant serum concentration and bioavailability of released hormones. By exploiting
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Implantable devices may provide a superior means for hormone delivery through maintaining serum levels within target therapeutic windows. Zero-order administration has been shown to reach an equilibrium with metabolic clearance, resulting in a constant serum concentration and bioavailability of released hormones. By exploiting surface-to-molecule interaction within nanochannel membranes, it is possible to achieve a long-term, constant diffusive release of agents from implantable reservoirs. In this study, we sought to demonstrate the controlled release of model hormones from a novel nanochannel system. We investigated the delivery of hormones through our nanochannel membrane over a period of 40 days. Levothyroxine, osteocalcin and testosterone were selected as representative hormones based on their different molecular properties and structures. The release mechanisms and transport behaviors of these hormones within 3, 5 and 40 nm channels were characterized. Results further supported the suitability of the nanochannels for sustained administration from implantable platforms. Full article
(This article belongs to the Special Issue Diffusion under Confinement in Nanopores)
Open AccessArticle Effect of Annealing Temperature and Oxygen Flow in the Properties of Ion Beam Sputtered SnO2x Thin Films
Materials 2015, 8(8), 5289-5297; doi:10.3390/ma8085243
Received: 30 June 2015 / Revised: 5 August 2015 / Accepted: 6 August 2015 / Published: 14 August 2015
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Abstract
Tin oxide (SnO2—x) thin films were prepared under various flow ratios of O2/(O2 + Ar) on unheated glass substrate using the ion beam sputtering (IBS) deposition technique. This work studied the effects of the flow ratio of O
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Tin oxide (SnO2—x) thin films were prepared under various flow ratios of O2/(O2 + Ar) on unheated glass substrate using the ion beam sputtering (IBS) deposition technique. This work studied the effects of the flow ratio of O2/(O2 + Ar), chamber pressures and post-annealing treatment on the physical properties of SnO2 thin films. It was found that annealing affects the crystal quality of the films as seen from both X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. In addition, the surface RMS roughness was measured with atomic force microscopy (AFM). Auger electron spectroscopy (AES) analysis was used to obtain the changes of elemental distribution between tin and oxygen atomic concentration. The electrical property is discussed with attention to the structure factor. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Effect of Stress Amplitude on the Damping of Recycled Aggregate Concrete
Materials 2015, 8(8), 5298-5312; doi:10.3390/ma8085242
Received: 23 July 2015 / Revised: 5 August 2015 / Accepted: 11 August 2015 / Published: 14 August 2015
Cited by 4 | PDF Full-text (577 KB) | HTML Full-text | XML Full-text
Abstract
Damping characterizes the energy dissipation capacity of materials and structures, and it is affected by several external factors such as vibrating frequency, stress history, temperature, and stress amplitude. This study investigates the relationship between the damping and the stress amplitude of environment-friendly recycled
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Damping characterizes the energy dissipation capacity of materials and structures, and it is affected by several external factors such as vibrating frequency, stress history, temperature, and stress amplitude. This study investigates the relationship between the damping and the stress amplitude of environment-friendly recycled aggregate concrete (RAC). First, a function model of a member’s loss factor and stress amplitude was derived based on Lazan’s damping-stress function. Then, the influence of stress amplitude on the loss tangent of RAC was experimentally investigated. Finally, parameters used to determine the newly derived function were obtained by numerical fitting. It is shown that the member’s loss factor is affected not only by the stress amplitude but also by factors such as the cross section shapes, boundary conditions, load types, and loading positions. The loss tangent of RAC increases with the stress amplitude, even at low stress amplitude. The damping energy exponent of RAC is not identically equal to 2.0, indicating that the damping is nonlinear. It is also found that the energy dissipation capacity of RAC is superior to that of natural aggregate concrete (NAC), and the energy dissipation capacity can be further improved by adding modified admixtures. Full article
Open AccessArticle Capacitive Behavior of Single Gallium Oxide Nanobelt
Materials 2015, 8(8), 5313-5320; doi:10.3390/ma8085244
Received: 4 June 2015 / Revised: 22 July 2015 / Accepted: 5 August 2015 / Published: 17 August 2015
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Abstract
In this research, monocrystalline gallium oxide (Ga2O3) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga2O3 nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate
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In this research, monocrystalline gallium oxide (Ga2O3) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga2O3 nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate the electrical characteristics of the Ga2O3 nanobelt in a dry atmosphere at room temperature. The current-voltage (I-V) and I/V-t characteristics show the capacitive behavior of the Ga2O3 nanobelt, indicating the existence of capacitive elements in the Pt/Ga2O3/Pt structure. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Investigation of Laminar Convective Heat Transfer for Al2O3-Water Nanofluids Flowing through a Square Cross-Section Duct with a Constant Heat Flux
Materials 2015, 8(8), 5321-5335; doi:10.3390/ma8085246
Received: 30 June 2015 / Revised: 4 August 2015 / Accepted: 10 August 2015 / Published: 19 August 2015
Cited by 7 | PDF Full-text (3284 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study is to numerically investigate the convective heat transfer of water-based Al2O3 nanofluids flowing through a square cross-section duct with a constant heat flux under laminar flow conditions. The effects of nanoparticle concentration and Peclet number on the heat
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The objective of this study is to numerically investigate the convective heat transfer of water-based Al2O3 nanofluids flowing through a square cross-section duct with a constant heat flux under laminar flow conditions. The effects of nanoparticle concentration and Peclet number on the heat transfer characteristics of Al2O3-water nanofluids are investigated. The nanoparticle diameter is 25 nm and six particle concentrations (0.2, 0.5, 1, 1.5, 2, and 2.5 vol.%) are considered. The numerical results show that the heat transfer coefficients and Nusselt numbers of Al2O3-water nanofluids increase with increases in the Peclet number as well as particle volume concentration. The heat transfer coefficient of nanofluids is increased by 25.5% at a particle volume concentration of 2.5% and a Peclet number of 7500 as compared with that of the base fluid (pure water). It is noteworthy that at the same particle volume concentration of 2.5%, the enhancement of the convective heat transfer coefficient of Al2O3-water nanofluid (25.5%) is much higher than that of the effective thermal conductivity (9.98%). Thus, the enhancement of the convective heat transfer cannot be solely attributed to the enhancement of the effective thermal conductivity. Additionally, the numerical results coincide well with the published experimental data. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Metal-Organic Frameworks to Metal/Metal Oxide Embedded Carbon Matrix: Synthesis, Characterization and Gas Sorption Properties
Materials 2015, 8(8), 5336-5347; doi:10.3390/ma8085245
Received: 5 July 2015 / Revised: 11 August 2015 / Accepted: 11 August 2015 / Published: 19 August 2015
Cited by 6 | PDF Full-text (4236 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three isostructural metal-organic frameworks, (MOFs), [Fe(OH)(1,4-NDC)] (1), [Al(OH)(1,4-NDC)] (2), and [In(OH)(1,4-NDC)] (3) have been synthesized hydrothermally by using 1,4-naphthalene dicarboxylate (1,4-NDC) as a linker. The MOFs were characterized using various techniques and further used as precursor materials for the synthesis of metal/metal oxide
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Three isostructural metal-organic frameworks, (MOFs), [Fe(OH)(1,4-NDC)] (1), [Al(OH)(1,4-NDC)] (2), and [In(OH)(1,4-NDC)] (3) have been synthesized hydrothermally by using 1,4-naphthalene dicarboxylate (1,4-NDC) as a linker. The MOFs were characterized using various techniques and further used as precursor materials for the synthesis of metal/metal oxide nanoparticles inserted in a carbon matrix through a simple thermal conversion method. The newly synthesized carbon materials were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy analysis, powder X-ray diffraction and BET analysis. The results showed that the MOF-derived carbon composite materials maintained the morphology of the original MOF upon carbonization, and confirmed the insertion of metal/metal oxide particles in the carbon matrix. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle Evaluation of Fatigue Strength Improvement by CFRP Laminates and Shot Peening onto the Tension Flanges Joining Corrugated SteelWebs
Materials 2015, 8(8), 5348-5362; doi:10.3390/ma8085248
Received: 5 June 2015 / Revised: 4 August 2015 / Accepted: 12 August 2015 / Published: 19 August 2015
Cited by 4 | PDF Full-text (2290 KB) | HTML Full-text | XML Full-text
Abstract
Corrugated steel web with inherent high out-of-plane stiffness has a promising application in configuring large span highway bridge girders. Due to the irregularity of the configuration details, the local stress concentration poses a major fatigue problem for the welded flange plates of high
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Corrugated steel web with inherent high out-of-plane stiffness has a promising application in configuring large span highway bridge girders. Due to the irregularity of the configuration details, the local stress concentration poses a major fatigue problem for the welded flange plates of high strength low alloy structural steels. In this work, the methods of applying CFRP laminate and shot peening onto the surfaces of the tension flanges were employed with the purpose of improving the fatigue strength of such configuration details. The effectiveness of this method in the improvement of fatigue strength has been examined experimentally. Test results show that the shot peening significantly increases hardness and roughness in contrast to these without treatment. Also, it has beneficial effects on the fatigue strength enhancement when compared against the test data of the joints with CFRP strengthening. The stiffness degradation during the loading progress is compared with each treatment. Incorporating the stress acting on the constituent parts of the CFRP laminates, a discussion is made regarding the mechanism of the retrofit and related influencing factors such as corrosion and economic cost. This work could enhance the understanding of the CFRP and shot peening in repairing such welded details and shed light on the reinforcement design of welded joints between corrugated steel webs and flange plates. Full article
Open AccessArticle Preparation of LuAG Powders with Single Phase and Good Dispersion for Transparent Ceramics Using Co-Precipitation Method
Materials 2015, 8(8), 5363-5375; doi:10.3390/ma8085247
Received: 8 June 2015 / Revised: 13 July 2015 / Accepted: 6 August 2015 / Published: 19 August 2015
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Abstract
The synthesis of pure and well dispersed lutetium aluminum garnet (LuAG) powder is crucial and important for the preparation of LuAG transparent ceramics. In this paper, high purity and well dispersed LuAG powders have been synthesized via co-precipitation method with lutetium nitrate and
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The synthesis of pure and well dispersed lutetium aluminum garnet (LuAG) powder is crucial and important for the preparation of LuAG transparent ceramics. In this paper, high purity and well dispersed LuAG powders have been synthesized via co-precipitation method with lutetium nitrate and aluminum nitrate as raw materials. Ammonium hydrogen carbonate (AHC) was used as the precipitant. The influence of aging time, pH value, and dripping speed on the prepared LuAG powders were investigated. It showed that long aging duration (>15 h) with high terminal pH value (>7.80) resulted in segregation of rhombus Lu precipitate and Al precipitate. By decreasing the initial pH value or accelerating the dripping speed, rhombus Lu precipitate was eliminated and pure LuAG nano powders were synthesized. High quality LuAG transparent ceramics with transmission >75% at 1064 nm were fabricated using these well dispersed nano LuAG powders. Full article
Open AccessArticle Towards Tuning the Mechanical Properties of Three-Dimensional Collagen Scaffolds Using a Coupled Fiber-Matrix Model
Materials 2015, 8(8), 5376-5384; doi:10.3390/ma8085254
Received: 24 June 2015 / Revised: 12 August 2015 / Accepted: 14 August 2015 / Published: 20 August 2015
Cited by 2 | PDF Full-text (3293 KB) | HTML Full-text | XML Full-text
Abstract
Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold
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Scaffold mechanical properties are essential in regulating the microenvironment of three-dimensional cell culture. A coupled fiber-matrix numerical model was developed in this work for predicting the mechanical response of collagen scaffolds subjected to various levels of non-enzymatic glycation and collagen concentrations. The scaffold was simulated by a Voronoi network embedded in a matrix. The computational model was validated using published experimental data. Results indicate that both non-enzymatic glycation-induced matrix stiffening and fiber network density, as regulated by collagen concentration, influence scaffold behavior. The heterogeneous stress patterns of the scaffold were induced by the interfacial mechanics between the collagen fiber network and the matrix. The knowledge obtained in this work could help to fine-tune the mechanical properties of collagen scaffolds for improved tissue regeneration applications. Full article
(This article belongs to the Section Biomaterials)
Open AccessArticle The π-Electron Delocalization in 2-Oxazolines Revisited: Quantification and Comparison with Its Analogue in Esters
Materials 2015, 8(8), 5385-5397; doi:10.3390/ma8085249
Received: 24 June 2015 / Accepted: 13 August 2015 / Published: 21 August 2015
Cited by 2 | PDF Full-text (1999 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The single crystal X-ray analysis of the ester-functionalized 2-oxazoline, methyl 3-(4,5-dihydrooxazol-2-yl)propanoate, revealed Π-electron delocalization along the N–C–O segment in the 2-oxazoline pentacycle to significant extent, which is comparable to its counterpart along the O–C–O segment in the ester. Quantum chemical calculations based on
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The single crystal X-ray analysis of the ester-functionalized 2-oxazoline, methyl 3-(4,5-dihydrooxazol-2-yl)propanoate, revealed Π-electron delocalization along the N–C–O segment in the 2-oxazoline pentacycle to significant extent, which is comparable to its counterpart along the O–C–O segment in the ester. Quantum chemical calculations based on the experimental X-ray geometry of the molecule supported the conjecture that the N–C–O segment has a delocalized electronic structure similar to an ester group. The calculated bond orders were 1.97 and 1.10 for the N=C and C–O bonds, and the computed partial charges for the nitrogen and oxygen atoms of \(-\)0.43 and \(-\)0.44 were almost identical. In the ester group, the bond orders were 1.94 and 1.18 for the C–O bonds, while the partial charges of the oxygen atom are \(-\)0.49 and \(-\)0.41, which demonstrates the similar electronic structure of the N–C–O and O–C–O segments. In 2-oxazolines, despite the higher electronegativity of the oxygen atom (compared to the nitrogen atom), the charges of the hetero atoms oxygen and nitrogen are equalized due to the delocalization, and it also means that a cationic attack on the nitrogen is possible, enabling regioselectivity during the initiation of the cationic ring-opening polymerization of 2-oxazoline monomers, which is a prerequisite for the synthesis of materials with well-defined structures. Full article
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Open AccessArticle On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials
Materials 2015, 8(8), 5398-5413; doi:10.3390/ma8085251
Received: 15 June 2015 / Revised: 21 July 2015 / Accepted: 17 August 2015 / Published: 21 August 2015
Cited by 4 | PDF Full-text (980 KB) | HTML Full-text | XML Full-text
Abstract
The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon
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The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90–0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example. Full article
Open AccessArticle Metal Nanoparticle-Decorated Two-Dimensional Molybdenum Sulfide for Plasmonic-Enhanced Polymer Photovoltaic Devices
Materials 2015, 8(8), 5414-5425; doi:10.3390/ma8085252
Received: 25 June 2015 / Revised: 6 August 2015 / Accepted: 18 August 2015 / Published: 21 August 2015
Cited by 2 | PDF Full-text (2029 KB) | HTML Full-text | XML Full-text
Abstract
Atomically thin two-dimensional (2D) transition metal dichalcogenides have also attracted immense interest because they exhibit appealing electronic, optical and mechanical properties. In this work, we prepared gold nanoparticle-decorated molybdenum sulfide (AuNP@MoS2) through a simple spontaneous redox reaction. Transmission electron microscopy, UV-Vis spectroscopy, and
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Atomically thin two-dimensional (2D) transition metal dichalcogenides have also attracted immense interest because they exhibit appealing electronic, optical and mechanical properties. In this work, we prepared gold nanoparticle-decorated molybdenum sulfide (AuNP@MoS2) through a simple spontaneous redox reaction. Transmission electron microscopy, UV-Vis spectroscopy, and Raman spectroscopy were used to characterize the properties of the AuNP@MoS2 nanomaterials. Then we employed such nanocomposites as the cathode buffer layers of organic photovoltaic devices (OPVs) to trigger surface plasmonic resonance, leading to noticeable enhancements in overall device efficiencies. We attribute the primary origin of the improvement in device performance to local field enhancement induced by the effects of localized surface plasmonic resonance. Our results suggest that the metal nanoparticle-decorated two-dimensional materials appear to have great potential for use in high-performance OPVs. Full article
(This article belongs to the Special Issue Plasmonic Materials)
Open AccessArticle Isolation and Characterization of Nano-Hydroxyapatite from Salmon Fish Bone
Materials 2015, 8(8), 5426-5439; doi:10.3390/ma8085253
Received: 5 June 2015 / Revised: 6 August 2015 / Accepted: 7 August 2015 / Published: 21 August 2015
Cited by 5 | PDF Full-text (8464 KB) | HTML Full-text | XML Full-text
Abstract
Nano-Hydroxyapatite (nHA) was isolated from salmon bone by alkaline hydrolysis. The resulting nHA was characterized using several analytical tools, including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to determine
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Nano-Hydroxyapatite (nHA) was isolated from salmon bone by alkaline hydrolysis. The resulting nHA was characterized using several analytical tools, including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), to determine the purity of the nHA sample. The removal of organic matter from the raw fish was confirmed by TGA. FT-IR confirmed the presence of a carbonated group and the similarities to synthetic Sigma HA. XRD revealed that the isolated nHA was amorphous. Microscopy demonstrated that the isolated nHA possessed a nanostructure with a size range of 6–37 nm. The obtained nHA interacted with mesenchymal stem cells (MSCs) and was non-toxic. Increased mineralization was observed for nHA treated MSCs compared to the control group. These results suggest that nHA derived from salmon is a promising biomaterial in the field of bone tissue engineering. Full article
Open AccessArticle Effects of Fiber Reinforcement on Clay Aerogel Composites
Materials 2015, 8(8), 5440-5451; doi:10.3390/ma8085258
Received: 2 July 2015 / Revised: 2 August 2015 / Accepted: 4 August 2015 / Published: 21 August 2015
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Abstract
Novel, low density structures which combine biologically-based fibers with clay aerogels are produced in an environmentally benign manner using water as solvent, and no additional processing chemicals. Three different reinforcing fibers, silk, soy silk, and hemp, are evaluated in combination with poly(vinyl alcohol)
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Novel, low density structures which combine biologically-based fibers with clay aerogels are produced in an environmentally benign manner using water as solvent, and no additional processing chemicals. Three different reinforcing fibers, silk, soy silk, and hemp, are evaluated in combination with poly(vinyl alcohol) matrix polymer combined with montmorillonite clay. The mechanical properties of the aerogels are demonstrated to increase with reinforcing fiber length, in each case limited by a critical fiber length, beyond which mechanical properties decline due to maldistribution of filler, and disruption of the aerogel structure. Rather than the classical model for reinforced composite properties, the chemical compatibility of reinforcing fibers with the polymer/clay matrix dominated mechanical performance, along with the tendencies of the fibers to kink under compression. Full article
(This article belongs to the Special Issue Green Composites)
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Open AccessArticle X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2
Materials 2015, 8(8), 5452-5466; doi:10.3390/ma8085255
Received: 30 July 2015 / Revised: 12 August 2015 / Accepted: 14 August 2015 / Published: 21 August 2015
Cited by 6 | PDF Full-text (387 KB) | HTML Full-text | XML Full-text
Abstract
Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the
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Epitaxial ultra-thin oxide films can support large percent level strains well beyond their bulk counterparts, thereby enabling strain-engineering in oxides that can tailor various phenomena. At these reduced dimensions (typically < 10 nm), contributions from the substrate can dwarf the signal from the epilayer, making it difficult to distinguish the properties of the epilayer from the bulk. This is especially true for oxide on oxide systems. Here, we have employed a combination of hard X-ray photoelectron spectroscopy (HAXPES) and angular soft X-ray absorption spectroscopy (XAS) to study epitaxial VO2/TiO2 (100) films ranging from 7.5 to 1 nm. We observe a low-temperature (300 K) insulating phase with evidence of vanadium-vanadium (V-V) dimers and a high-temperature (400 K) metallic phase absent of V-V dimers irrespective of film thickness. Our results confirm that the metal insulator transition can exist at atomic dimensions and that biaxial strain can still be used to control the temperature of its transition when the interfaces are atomically sharp. More generally, our case study highlights the benefits of using non-destructive XAS and HAXPES to extract out information regarding the interfacial quality of the epilayers and spectroscopic signatures associated with exotic phenomena at these dimensions. Full article
(This article belongs to the Special Issue Epitaxial Materials 2015)
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Open AccessArticle Fabrication of CH3NH3PbI3/PVP Composite Fibers via Electrospinning and Deposition
Materials 2015, 8(8), 5467-5478; doi:10.3390/ma8085256
Received: 10 June 2015 / Revised: 5 August 2015 / Accepted: 14 August 2015 / Published: 21 August 2015
Cited by 3 | PDF Full-text (7106 KB) | HTML Full-text | XML Full-text
Abstract
In our study, one-dimensional PbI2/polyvinylpyrrolidone (PVP) composition fibers have been prepared by using PbI2 and PVP as precursors dissolved in N,N-dimethylformamide via a electrospinning process. Dipping the fibers into CH3NH3I solution changed its
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In our study, one-dimensional PbI2/polyvinylpyrrolidone (PVP) composition fibers have been prepared by using PbI2 and PVP as precursors dissolved in N,N-dimethylformamide via a electrospinning process. Dipping the fibers into CH3NH3I solution changed its color, indicating the formation of CH3NH3PbI3, to obtain CH3NH3PbI3/PVP composite fibers. The structure, morphology and composition of the all as-prepared fibers were characterized by using X-ray diffraction and scanning electron microscopy. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Recyclability of Concrete Pavement Incorporating High Volume of Fly Ash
Materials 2015, 8(8), 5479-5489; doi:10.3390/ma8085260
Received: 27 July 2015 / Revised: 14 August 2015 / Accepted: 17 August 2015 / Published: 21 August 2015
Cited by 2 | PDF Full-text (338 KB) | HTML Full-text | XML Full-text
Abstract
Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the
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Recyclable concrete pavement was made from fly ash and crushed limestone sand and gravel as aggregates so that the concrete pavement could be recycled to raw materials for cement production. With the aim to use as much fly ash as possible for the sustainable development of society, while achieving adequate strength development, pavement concrete having a cement-replacement ratio of 40% by mass was experimentally investigated, focusing on the strength development at an early age. Limestone powder was added to improve the early strength; flexural strength at two days reached 3.5 MPa, the minimum strength for traffic service in Japan. The matured fly ash concrete made with a cement content of 200 kg/m3 achieved a flexural strength almost equal to that of the control concrete without fly ash. Additionally, Portland cement made from the tested fly ash concrete was tested to confirm recyclability, with the cement quality meeting the Japanese classification of ordinary Portland cement. Limestone-based recyclable fly ash concrete pavement is, thus, a preferred material in terms of sustainability. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
Open AccessArticle Influence of Different Three-Dimensional Open Porous Titanium Scaffold Designs on Human Osteoblasts Behavior in Static and Dynamic Cell Investigations
Materials 2015, 8(8), 5490-5507; doi:10.3390/ma8085259
Received: 26 May 2015 / Revised: 30 July 2015 / Accepted: 13 August 2015 / Published: 24 August 2015
Cited by 7 | PDF Full-text (16532 KB) | HTML Full-text | XML Full-text
Abstract
In the treatment of osseous defects micro-structured three-dimensional materials for bone replacement serve as leading structure for cell migration, proliferation and bone formation. The scaffold design and culture conditions are crucial for the limited diffusion distance of nutrients and oxygen. In static culture,
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In the treatment of osseous defects micro-structured three-dimensional materials for bone replacement serve as leading structure for cell migration, proliferation and bone formation. The scaffold design and culture conditions are crucial for the limited diffusion distance of nutrients and oxygen. In static culture, decreased cell activity and irregular distribution occur within the scaffold. Dynamic conditions entail physical stimulation and constant medium perfusion imitating physiological nutrient supply and metabolite disposal. Therefore, we investigated the influence of different scaffold configurations and cultivation methods on human osteoblasts. Cells were seeded on three-dimensional porous Ti-6Al-4V scaffolds manufactured with selective laser melting (SLM) or electron beam melting (EBM) varying in porosity, pore size and basic structure (cubic, diagonal, pyramidal) and cultured under static and dynamic conditions. Cell viability, migration and matrix production were examined via mitochondrial activity assay, fluorescence staining and ELISA. All scaffolds showed an increasing cell activity and matrix production under static conditions over time. Expectations about the dynamic culture were only partially fulfilled, since it enabled proliferation alike the static one and enhanced cell migration. Overall, the SLM manufactured scaffold with the highest porosity, small pore size and pyramidal basic structure proved to be the most suitable structure for cell proliferation and migration. Full article
(This article belongs to the Section Porous Materials)
Open AccessArticle The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation
Materials 2015, 8(8), 5508-5525; doi:10.3390/ma8085257
Received: 15 June 2015 / Revised: 31 July 2015 / Accepted: 10 August 2015 / Published: 24 August 2015
Cited by 2 | PDF Full-text (5121 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using
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Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region. Full article
Open AccessArticle Thermal and Mechanical Behavior of Hybrid Polymer Nanocomposite Reinforced with Graphene Nanoplatelets
Materials 2015, 8(8), 5526-5536; doi:10.3390/ma8085262
Received: 21 June 2015 / Revised: 4 August 2015 / Accepted: 19 August 2015 / Published: 24 August 2015
Cited by 8 | PDF Full-text (2814 KB) | HTML Full-text | XML Full-text
Abstract
In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is
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In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is then mixed with a hardener using a high-speed mechanical stirrer. The trapped air and reaction volatiles are removed from the mixture using high vacuum. The hot press casting method is used to make the nanocomposite specimens. Tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are performed on neat, 0.2 wt %, 0.5 wt %, 1 wt %, 1.5 wt % and 2 wt % GNP-reinforced epoxy/polyester blend resin to investigate the reinforcement effect on the thermal and mechanical properties of the nanocomposites. The results of this research indicate that the tensile strength of the novel nanocomposite material increases to 86.8% with the addition of a ratio of graphene nanoplatelets as low as 0.2 wt %. DMA results indicate that the 1 wt % GNP-reinforced epoxy/polyester nanocomposite possesses the highest storage modulus and glass transition temperature (Tg), as compared to neat epoxy/polyester or the other nanocomposite specimens. In addition, TGA results verify thethermal stability of the experimental specimens, regardless of the weight percentage of GNPs. Full article
(This article belongs to the Special Issue Selected Papers from ICASI 2015)
Open AccessArticle Early-Age Strength of Ultra-High Performance Concrete in Various Curing Conditions
Materials 2015, 8(8), 5537-5553; doi:10.3390/ma8085261
Received: 11 July 2015 / Revised: 4 August 2015 / Accepted: 7 August 2015 / Published: 24 August 2015
Cited by 6 | PDF Full-text (1260 KB) | HTML Full-text | XML Full-text
Abstract
The strength of Ultra-High Performance Concrete (UHPC) can be sensitively affected by the curing method used. However, in contrast to the precast plant production of UHPC where a standard high-temperature steam curing is available, an optimum curing condition is rarely realized with cast-in-place
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The strength of Ultra-High Performance Concrete (UHPC) can be sensitively affected by the curing method used. However, in contrast to the precast plant production of UHPC where a standard high-temperature steam curing is available, an optimum curing condition is rarely realized with cast-in-place UHPC. Therefore, the trend of the compressive strength development of UHPC was experimentally investigated in this study, with a focus on early-age strength by assuming the various curing conditions anticipated on site. Concrete specimens were cured under different conditions with variables including curing temperature, delay time before the initiation of curing, duration of curing, and moisture condition. Several conditions for curing are proposed that are required when the cast-in-place UHPC should gain a specified strength at an early age. It is expected that the practical use of UHPC on construction sites can be expedited through this study. Full article
(This article belongs to the Section Advanced Composites)

Review

Jump to: Research

Open AccessReview Mineralized Collagen: Rationale, Current Status, and Clinical Applications
Materials 2015, 8(8), 4733-4750; doi:10.3390/ma8084733
Received: 16 May 2015 / Revised: 29 June 2015 / Accepted: 13 July 2015 / Published: 24 July 2015
Cited by 14 | PDF Full-text (2470 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a review of the rationale for the in vitro mineralization process, preparation methods, and clinical applications of mineralized collagen. The rationale for natural mineralized collagen and the related mineralization process has been investigated for decades. Based on the understanding of
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This paper presents a review of the rationale for the in vitro mineralization process, preparation methods, and clinical applications of mineralized collagen. The rationale for natural mineralized collagen and the related mineralization process has been investigated for decades. Based on the understanding of natural mineralized collagen and its formation process, many attempts have been made to prepare biomimetic materials that resemble natural mineralized collagen in both composition and structure. To date, a number of bone substitute materials have been developed based on the principles of mineralized collagen, and some of them have been commercialized and approved by regulatory agencies. The clinical outcomes of mineralized collagen are of significance to advance the evaluation and improvement of related medical device products. Some representative clinical cases have been reported, and there are more clinical applications and long-term follow-ups that currently being performed by many research groups. Full article
(This article belongs to the Special Issue Novel Bone Substitute Materials)
Open AccessReview Preclinical in vivo Performance of Novel Biodegradable, Electrospun Poly(lactic acid) and Poly(lactic-co-glycolic acid) Nanocomposites: A Review
Materials 2015, 8(8), 4912-4931; doi:10.3390/ma8084912
Received: 26 June 2015 / Revised: 26 June 2015 / Accepted: 24 July 2015 / Published: 3 August 2015
Cited by 6 | PDF Full-text (864 KB) | HTML Full-text | XML Full-text
Abstract
Bone substitute materials have witnessed tremendous development over the past decades and autogenous bone may still be considered the gold standard for many clinicians and clinical approaches in order to rebuild and restore bone defects. However, a plethora of novel xenogenic and synthetic
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Bone substitute materials have witnessed tremendous development over the past decades and autogenous bone may still be considered the gold standard for many clinicians and clinical approaches in order to rebuild and restore bone defects. However, a plethora of novel xenogenic and synthetic bone substitute materials have been introduced in recent years in the field of bone regeneration. As the development of bone is actually a calcification process within a collagen fiber arrangement, the use of scaffolds in the formation of fibers may offer some advantages, along with additional handling characteristics. This review focuses on material characteristics and degradation behavior of electrospun biodegradable polyester scaffolds. Furthermore, we concentrated on the preclinical in vivo performance with regard to bone regeneration in preclinical studies. The major findings are as follows: Scaffold composition and architecture determine its biological behavior and degradation characteristics; The incorporation of inorganic substances and/or organic substances within composite scaffolds enhances new bone formation; L-poly(lactic acid) and poly(lactic-co-glycolic acid) composite scaffolds, especially when combined with basic substances like hydroxyapatite, tricalcium phosphate or demineralized bone powder, seem not to induce inflammatory tissue reactions in vivo. Full article
(This article belongs to the Special Issue Novel Bone Substitute Materials)
Open AccessReview Zirconia as a Dental Biomaterial
Materials 2015, 8(8), 4978-4991; doi:10.3390/ma8084978
Received: 24 June 2015 / Accepted: 30 July 2015 / Published: 4 August 2015
Cited by 8 | PDF Full-text (498 KB) | HTML Full-text | XML Full-text
Abstract
Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges,
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Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different substrates, which has offered a great challenge to dental zirconia research and development. This study characterizes zirconia as a dental biomaterial, presenting the current consensus and challenges to its dental applications. Full article
(This article belongs to the Special Issue Bioceramics)
Open AccessReview The Role of Computer Simulation in Nanoporous Metals—A Review
Materials 2015, 8(8), 5060-5083; doi:10.3390/ma8085060
Received: 7 July 2015 / Revised: 7 July 2015 / Accepted: 4 August 2015 / Published: 7 August 2015
Cited by 6 | PDF Full-text (3106 KB) | HTML Full-text | XML Full-text
Abstract
Nanoporous metals (NPMs) have proven to be all-round candidates in versatile and diverse applications. In this decade, interest has grown in the fabrication, characterization and applications of these intriguing materials. Most existing reviews focus on the experimental and theoretical works rather than the
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Nanoporous metals (NPMs) have proven to be all-round candidates in versatile and diverse applications. In this decade, interest has grown in the fabrication, characterization and applications of these intriguing materials. Most existing reviews focus on the experimental and theoretical works rather than the numerical simulation. Actually, with numerous experiments and theory analysis, studies based on computer simulation, which may model complex microstructure in more realistic ways, play a key role in understanding and predicting the behaviors of NPMs. In this review, we present a comprehensive overview of the computer simulations of NPMs, which are prepared through chemical dealloying. Firstly, we summarize the various simulation approaches to preparation, processing, and the basic physical and chemical properties of NPMs. In this part, the emphasis is attached to works involving dealloying, coarsening and mechanical properties. Then, we conclude with the latest progress as well as the future challenges in simulation studies. We believe that highlighting the importance of simulations will help to better understand the properties of novel materials and help with new scientific research on these materials. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
Open AccessReview Smart Dressings Based on Nanostructured Fibers Containing Natural Origin Antimicrobial, Anti-Inflammatory, and Regenerative Compounds
Materials 2015, 8(8), 5154-5193; doi:10.3390/ma8085154
Received: 4 July 2015 / Revised: 30 July 2015 / Accepted: 5 August 2015 / Published: 11 August 2015
Cited by 10 | PDF Full-text (2233 KB) | HTML Full-text | XML Full-text
Abstract
A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients’ quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds.
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A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients’ quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds. In spite of all the efforts that have been made during the recent years towards the development of artificial wound dressings, none of the currently available options combine all the requirements necessary for quick and optimal cutaneous regeneration. Therefore, technological advances in the area of temporary and permanent smart dressings for wound care are required. The development of nanoscience and nanotechnology can improve the materials and designs used in topical wound care in order to efficiently release antimicrobial, anti-inflammatory and regenerative compounds speeding up the endogenous healing process. Nanostructured dressings can overcome the limitations of the current coverings and, separately, natural origin components can also overcome the drawbacks of current antibiotics and antiseptics (mainly cytotoxicity, antibiotic resistance, and allergies). The combination of natural origin components with demonstrated antibiotic, regenerative, or anti-inflammatory properties together with nanostructured materials is a promising approach to fulfil all the requirements needed for the next generation of bioactive wound dressings. Microbially compromised wounds have been treated with different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring antimicrobial, anti-inflammatory, and regenerative components but the available evidence is limited and insufficient to be able to draw reliable conclusions and to extrapolate those findings to the clinical practice. The evidence and some promising preliminary results indicate that future comparative studies are justified but instead of talking about the beneficial or inert effects of those natural origin occurring materials, the scientific community leads towards the identification of the main active components involved and their mechanism of action during the corresponding healing, antimicrobial, or regenerative processes and in carrying out systematic and comparative controlled tests. Once those natural origin components have been identified and their efficacy validated through solid clinical trials, their combination within nanostructured dressings can open up new avenues in the fabrication of bioactive dressings with outstanding characteristics for wound care. The motivation of this work is to analyze the state of the art in the use of different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring materials as antimicrobial, anti-inflammatory and regenerative components with the aim of clarifying their potential clinical use in bioactive dressings. We conclude that, for those natural occurring materials, more clinical trials are needed to reach a sufficient level of evidence as therapeutic agents for wound healing management. Full article
(This article belongs to the Special Issue Therapeutics Delivery Systems for Regenerative Nanomedicine)

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